1. Field of the Invention
The present invention relates to a method and apparatus for judging presence of a position shift of a sample material with respect to a sample table.
2. Description of the Related Art
Conventionally, an apparatus for assaying (quantitatively measuring), based on time-course data, chemical components contained in blood is well known. In the apparatus, blood is dripped into a reaction cell in which a reagent has been deposited, and the reagent and the blood are reacted with each other. Then, time-course data is obtained by measuring, in time series, a change in the density of a sample material that contains the reagent and the blood. As such an apparatus, an apparatus that simultaneously assays a plurality of components, such as glucose and calcium, contained in blood by using reagents, such as a reagent for assaying glucose and a reagent for assaying calcium, respectively is well known. For example, an apparatus in which a plurality of reaction cells are placed on a sample table along the circumference thereof is well known. In the apparatus, sample materials that are different from each other are deposited in the plurality of reaction cells, and these reaction cells are rotated by rotating the sample table. While the reaction cells are rotated, an optical meter that has been fixed to a certain position repeatedly measures a change in the density of each of the sample materials at regular intervals, for example, every eight seconds. Accordingly, time-course data is obtained.
In the apparatus in which a change in the density of a sample material is repeatedly measured while the reaction cells placed along the circumference of the sample table are rotated, as described above, the position of the sample material with respect to the sample table is shifted (incorrectly positioned) in some cases. When a sample material is repeatedly measured, if the position of the sample material is shifted, the accuracy in measurement of a change in the density of the sample material becomes lower. Therefore, obtained time-course data indicates an abnormal value.
As a method for judging the abnormality of the time-course data, a method in which when it is expected that the density of the sample material will not reach a predetermined density within a predetermined time period, it is judged that the time-course data is abnormal is well known. In this method, if the time-course data is judged to be abnormal, the measurement is stopped before completion, and measurement is carried out again (please refer to Japanese Unexamined Patent Publication No. 6 (1994)-034638).
In the apparatus that measures each of a plurality of sample materials in time series by repeatedly conveying each of the plurality of sample materials to a measurement position by movement of a sample table on which the plurality of sample materials are placed, abnormality of time-course data is caused by a shift in the position of a sample material with respect to the sample table in most cases. Therefore, presence of a position shift of a sample material with respect to the sample table (in other words, whether the position of a sample material is shifted with respect to the position of the sample table) may be judged by judging whether the time-course data is abnormal or not.
However, the fluctuation of the time-course data that is caused by the shift in the position of the sample material with respect to the sample table has various kinds of patterns. Therefore, if the abnormality of the time-course data is judged only based on whether the density of a sample material has reached a predetermined density within a predetermined time period, abnormality is not detected in some cases. Hence, it is impossible to accurately distinguish normal time-course data and abnormal time-course data from each other in some cases. Specifically, it is impossible to accurately judge presence of a shift in the position of a sample material with respect to the sample table by using the time-course data in some cases.